Early entry and deformation of macropinosomes correlates with high efficiency of decaarginine-polyethylene glycol-lipid-mediated gene delivery

Background Decaarginine-polyethylene glycol-conjugated 3,5-bis(dodecyloxy)benzamide/plasmid DNA [Arg10-polyethylene glycol (PEG)-lipid/plasmid DNA (pDNA)] complexes (designated R10B/DNA complexes) are efficient nonviral carriers for pDNA delivery into human cervical carcinoma HeLa cells. Previous reports indicated that these complexes formed at a relatively low R10B/DNA ratio and showed high transgene expression efficiency. However, the intracellular behaviour of the two different nanostructures, which leads to differences in gene delivery, remains to be elucidated. Methods R10B/DNA complexes prepared at a N/P ratio of 8.5/1 or 42.5/1, corresponding to 5 mu M or 25 mu M R10B, respectively, were added to HeLa cells, and their uptake and subsequent intracellular fate were examined by cell imaging using electronmicroscopy (EM) and correlative light-electronmicroscopy (CLEM). Results EM and CLEManalyses revealed that R10B/DNA complexes formed at the lower N/P ratio were mainly taken up by the cells through macropinocytosis, whereas R10B/DNA complexes formed at the higher N/P ratio bound to protruding membrane structures or permeated into the cells by a different pathway. In cells expressing the transgene, R10B/DNA complexes were observed both in macropinosomes and in the cytoplasm. In addition, these cells had macropinosomes with disrupted membranes. These results suggest that cellular uptake through macropinocytosis and subsequent disruption of the macropinosome membrane may be a critical step for R10B-mediated gene delivery. Conclusions We have shown that the existence of R10B/DNA complexes in macropinosomes at the early stages of gene delivery correlates with high efficiency R10B-mediated gene delivery. This finding will provide valuable insights for the engineering of more efficient gene delivery systems based on oligoarginine-mediated carriers. Copyright (C) 2012 John Wiley & Sons, Ltd.